Rotary joints are used in a variety of different applications including construction machinery, rotary cranes, and frequently also in wind power plants, although the uses are not limited in this regard. In such cases, it is generally necessary with the use of a generic rotary joint, in addition to effecting the rotatable connection of two machine or system parts, to also transfer for the active rotation of one of the two machine or system parts, a drive moment to this machine or system part, with the drive moment being usually provided by an electric or hydraulic drive.
German Offenlegungsschrift No. DE 198 14 629 A1 discloses an arrangement for rotatably positioning the machine pod of a wind power plant. The torque is transferred from the rotatable machine pod to the fixed tower by way of electromotive drives. Each of the drives is provided with a toothed gear pinion, each of which engages an encircling toothing disposed on the tower or on the fixed bearing ring of the rotary joint, whereby the motor rotation of the machine pod relative to the tower is made possible.
A generic rotary joint formed in this way is, however, laborious and thus expensive to manufacture, and also has a significant maintenance requirement. This maintenance includes the regular lubrication or cyclical cleaning of the toothed gear and the drive pinion. Beyond this, as for all toothed gears, the toothing of the pinion and the toothed ring must be aligned very precisely relative to one another to avoid reductions in the life and/or provide security against failure of the drive.
The high expenditure in production of a rotary joint of this type arises by virtue of the production of the toothing of the encircling toothed gear and also the production of the toothing on the drive pinion(s). This is so because the toothing of the toothed rim of the drive must be milled in a known, laborious manner with precision tools and subsequently subjected to heat treatment for tempering the edges of the teeth. In a similar manner, the toothing of the drive pinion must also be produced and heat-treated. Moreover, a torque transfer of this type requires, on account of the toothed gear, the pinion and the assigned drive motors, a not insignificant space in the immediate area of the rotary joint. Such space is not available in all cases.
A need thus exists for a rotary joint which allows a drive moment to be transferred to one of the bearing rings, yet which can be more cost-effectively produced. It would also be desirable to provide a rotary joint which requires relatively small mounting and maintenance expense, while also permitting greater flexibility relative to the arrangement of the torque-generating and torque-transferring machine elements.